Commutator having disc-shaped base



Nov. 3, 1970 y L.. RElsNEcKER 3,538,365

COMMUTATOR HAVING DISC SHAPED BASE med Aug. 21. 196'/ United States Patent O1' hee 3,538,365 Patented Nov. 3, 1970 COMMUTATOR HAVING DISC-SHAPED BASE Ludwig Reisnecker, Rommelshausen, Germany, asslgnor to Robert Bosch G.m.b.H., Stuttgart, Germany Filed Aug. 21, 1967, Ser. No. 662,097 Claims priority, applicatgtgn7gsermany, Sept. 1, 1966,

1m. C1. Hir 39/06 U.S. Cl. 310-237 2 Claims A `ABSTRACT oF THE DISCLOSURE BACKGROUND OF THE INVENTION The present invention relates to a commutator for electrical motors. More particularly, the present invention relates to a commutator which is particularly suitable for starter motors and generators of motor vehicles. Still more specifically, the present invention relates to a commutator whose lamellas extend at a major surface of a disk-shaped lbase member of insulating material in a direction normal to the commutator axis.

Commutators of the general type here under discussion are known in the art. In this type of commutators the commutator lamellas must be so constructed that they will be able to withstand the electrical load requirements and the mechanical deterioration which results from contact with the brushes for a specified period, that `is for the lifetime which has been selected for the commutator. Furthermore, it is necessary that these lamellas be reliably anchored to the commutator base member. For this latter purpose it is known from the art to provide the commutator lamellas, which consist of copper, on that side which overlies the base member of insulating material with projections which can grip the material of the base member. These projections are in form of massive claws or the like.

' Copper, however, is a relativelycexpensive raw material and to make the anchoring projections of massive copper is economically highly disadvantageous, quite aside from the fact that the strength of these copper anchoring projections is not adequate for providing satisfactory anchoring of the lamellas in the base member.

SUMMARY OF THE INVENTION i The present invention overcomes these disadvantages.

More particularly, the present invention provides a commutator in which the lamellas are firmly anchored in the base member.

In the commutator according to the present invention the quantity of copper required is reduced considerably because copperv is no longer used for anchoring purposes.

My novel commutator employs copper only for the actual commutator lamellas, so that the quantity of copper. required for each lamella is determined solely with a View towards the electrical load the lamella is required to carry and towards the mechanical wear which the lamella undergoes as a result of contact by the brushes.

In accordance with one feature of my invention I provide a commutator for electrical motors which has particular utility for starter motors and for the generator of motor vehicles, although its usefulness is of course not limited in this manner. My novel commutator cornprises a disk-shaped base member of insulating material which has a major surface, and a plurality of commutator lamellas which overlie this major surface and which are ararnged thereon circumferentially spaced from each other. Thus far the construction is conventional.

In accordance with my invention, however, each of the commutator lamellas consists of a steel segment which overlies the major surface of the base member and which is at least partially embedded in the insulating material of this member, and of a copper segment which overlies the respective steel segment and which is rigid therewith.

Thus, the copper segment can be tailored exclusively with a view towards the electrical load which it must carry and with a view towards the mechanical wear which it will undergo because of its contact with the brushes. None of the copper of the copper segments is utilized for anchoring the segments in the base member, and a savingfin copper is thereby clearly effected. The anchoring of the segments is provided by the steel segments of which one is assigned to each of the copper segments, constituting together with the same the commutator lamellas.

In constructing the novel commutator which -I have disclosed I employ a method according to which I form a circular steel blank, which is preferably of annular configuration, with a plurality of circumferentially spaced radially extending slots intermediate the center and the outer peripheral edge of the blank. In other words, the slots will terminate inwardly of the outer edge and outwardly of the center or, if the blank is annular, of the center opening of the blank. I thus obtain a plurality of Wedge-shaped steel segments which are connected at their radially inner and radially outer ends.

Thereupon, a stamp from each of the thus obtained segments at least one anchoring strip portion which is connected with one end to the respective segment and which also has a free end. I bend this strip portion so that the free end projects to one side of the general plane of the steel blank. Once this is done, I rigidly conductively secure to one exposed face of the steel blank, namely that face which is opposite the one side to which the free ends of the anchoring strip portions project, an annular copper blank which has a smaller overall diameter than the steel blank. This securing can be effected in a number of ways, and I prefer to utilize soldering as an effective means. -By making the copper blank of a smaller overall diameter and, if the steel blank is also of annular configuration, by making the copper blank of a large inner diameter than that of the steel blank, I assure that the portions of the steel blank at which the Wedge-shaped steel segments are connected at their radially innermost and radially outermost ends are located beyond the inner and outer peripheral edges of the copper blank. I then sever the material of the steel blank along two circular lines which respectively intersect the radially innermost and the radially outermost ends of the slots in the steel blank and thereby separate the wedge-shaped segments from one another. Now, I bend the radially innermost edge portions of the segments so that they extend to the aforementioned one side of the general plane of the steel blank, and I embed the anchoring strip portions and the radially innermost edge portions in the disc-shaped base member of insulating material. Finally, I sever the material of the copper blank along radial lines each of which coincides with one of the slots and I have now obtained a plurality of lamellas, each of which consists of a wedgeshaped copper segment rigidly secured in conductive relationship to a wedge-shaped steel segment which in turn is partially embedded in the insulating material of the disc-shaped base member.

With this construction the anchoring of each lamella is effected, as is obvious, by embedding of the portions of the steel segments in the material of the base member. Of course, the steel has much greater strength than the copper and the lamellas are thus secured much more reliably than was the case previously when the embedding portions consisted of copper. Furthermore, the steel is significantly less expensive than copper so that my overall construction is cheaper to manufacture and therefore to sell than was known with the constructions from the prior art.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, to-

' gether with additional objects and advantages thereof,

will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partially sectioned perspective view illustrating a commutator embodying my invention;

FIG. 2 is a steel blank from which the wedge-shaped steel segments are to be made;

FIG. 3 is a section taken on the line III-III of FIG. 2, but showing not only the steel blank but also the superimposed copper blank; and

FIG. 4 illustrates in sectional view the copper and steel blanks with the wedge-shaped segments of the latter separated from one another.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing now the drawing in detail, and firstly the perspective view of FIG. l, it will be seen that my novel commutator is generally identified with reference numeral 10. It comprises a disk-shaped base member 11 of a suitable insulating material. A variety of such materials are well known to those skilled in the art and it is therefore not believed necessary to discuss the material in greater detail beyond stating that it must evidently be possessed of electrically insulating characteristics.

In the illustrated embodiment it will be seen that the base member 11, which is annular, carries on one of its major surfaces a plurality of circumferentially spaced lamellas 12 each of which consists of a wedge-shaped steel segment 13 having soldered thereon, for instance by hard soldering, a similarly wedge-shaped copper segment 14. The sectioned portion of FIG. 1 indicates that the steel segments 13 are provided with an anchoring strip portion 15 which is stamped from the material of the segments, and that the radially innermost end portion of each of the segments 13, identified with reference numeral 15 in FIG. 1, is similarly bent out of the general plane of the respective section 13. The portions 15 and 15 are embedded in the material of the base member 11 and thus reliably and rigidly secure each of the steel segments to this member 11.

FIG. 1 also shows that at the outer peripheral edge of the commutator the lamellas 12 are each provided with a slot 16 for facilitating solder connection of the armature, winding terminals of an electric motor, which latter is not illustrated as not constituting a part of the invention. The central aperture, that is the hub portion of the base member 11, is reinforced in a suitable manner, for instance by having a reinforcing sleeve .17 embedded therein.

FIGS. 2-4 illustrate various steps in the manufacture of the commutator illustrated in FIG. 1. FIG. 2 shows an annular steel blank 18` which is provided with a plurality of radially extending slots 13', of which only some are shown in FIG. 2. These slots can be formed in various different ways, and preferably are provided by stamping strips of material out of the blank 18. It will be seen that the slots 13 terminate inwardly of the respective inner and outer circumferential edge portions of the blank 18 and that, by providing the slots 13, I provide a plurality of adjacent wedge-shaped segments 13 of which FIG. 2 again shows only a few. Each of these segments 13" is in turn provided with an anchoring strip portion 15, for instance by stamping a portion of each of the segments 13 out of the general plane of the respective segment. Thus, the free ends of the anchoring strip portions 15 extend to one side of this general plane. To facilitate positioning of the blank 18 during subsequent operations, -it is advisable to provide several guide projections, and FIG. 2 shows four such circumferentially spaced guide projections 19 which are stamped out of the material of the blank 18 so that they project on the side of the blank 18 which is opposite the side on which the free ends of the anchoring strip portions `15 project.

FIG. 3 shows that at this manufacturing stage a blank 20 of copper is placed onto the blank 18. The blank 20 is also of annular configuration and there will be seen that both its inner and its outer diameter differ from the corresponding dimensions of the blank 18, the inner diameter of the blank 20 being larger than the corresponding inner diameter of the blank 18, and the outer diameter of the blank 20 being smaller than the outer diameter of the blank 18. The guide projections 19 on the blank 18 are so arranged that, when the blank 20 is placed onto the blank 18, it will be located within the confines of the guide projections 19 and will thus be held against shifting with reference to the blank 18. Thereupon, the blanks 18 and 20 are suitably conductively connected to one another, for instance by hard soldering in a protective gas.

Once the blanks 18 and 20 are connected to one another the segments 13 are separated from one another by severing the material of the blank 18 along the circular lines which respectively intersect the radially outermost and radially innermost ends of the slots 13. By so doing the radially innermost end portions of each of the segments `13", namely the portions 15', are freed and they are now bent rearwardly out of the general plane of the respective segments, that is to that side to which the anchoring strip portions 15 have previously been bent. This is clearly evident from FIG. 4.

The semi-finished assembly of FIG. 4 is now ready for joining to the base member 11. This can be effected in a variety of ways all of which lare well known in the art. By way of example it could be mentioned that the assembly of FIG. 4 can simply be placed into a press in which it lis united with insulating material which is formed by the press into the configuration of the base member 11. In any case, the portions 15 and 15' are embedded in the insulating material of the member 11 in the manner shown in FIG. l. The radially outermost end portion of each of the steel segments 13 is thereupon provided, preferably centrally in the manner shown in FIG. l, with a slot 16 by stamping or in a similar fashion. This slot serves to facilitate soldering or otherwise securing auxiliary components to the commutator, for instance the armature-winding ends of the afore` mentioned non-illustrated electric motor. Finally, the copper blank 20 is severed-by sawing or in another suitable manner-along lines each of which coincides with one of the slots 13' whereby the copper blank 20 is separated into individual copper segments 14. Each of the copper segments `14 is thus secured by soldering or in another manner to one of the steel segments 13", or 13 as indicated in FIG. 1, and constitutes together Iwith the steel segment a commutator lamella 12.

It is clear that with the construction disclosed herein the copper required in each Of the lamellas 12 is needed only for carrying the required electrical load and for withstanding the mechanical wear resulting from contact with the brushes, while it is no longer required to aid in anchoring the lamellas in the base member 11, a task which is now performed by the steel segments 13 at lesser cost and more reliably than was the case heretofore when it was portions of the copper lamellas which were thus embedded.

It will be understood that each of the elements described above, or'two or more together, may also find a useful application in other types of commutators differing from the types described above.

While the invention has been illustrated and described as embodied in a commutator for electrical motors, it is not intended to be limited to the details sho'wn, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that other can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or speciiic aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A commutator 'for electric motors, particularly for starter mortors and for generators of motor vehicles, comprising a disc-shaped base member consisting of insulating material and having a major surface, a circum- `ferential edge portion and an apertured hub portion; and

a plurality of commutator lamellas overlying said major surface and arrayed thereon circumferentially spaced from each other, each of said lamellas comprising a steel segment adjacent to said major surface and having a pair of anchoring portions embedded in said base member and spaced radially from one another, and a copper segment rigid with that side of the respective steel segment which faces away from said major surface and bridging the space between the anchoring portions of the respective steel segment, each of said lamellas extending from said hub portion to said edge portion and being provided in the region of said edge portion with a slot for facilitating bonding of auxiliary components to the respective lamellas.

2. A commutator as defined in claim 1, wherein said steel segments each have a radially inner end portion adjacent said hub portion of said base member, and a radially outer end portion adjacent to said circumferential edge portion of said base member, said end portions constituting said anchoring portions.

References Cited UNITED STATES PATENTS 1,219,565 3/1917 Kouyoumjian 310-237 1,537,692 5/1925 Prouty 310-237 3,165,828 1/1965 Kennedy 29-196.3 3,244,917 4/1966 Gute 310-237 3,298,803 l/l967 Ulam 29-196.3

MILTON O. HIRSHFIELD, Primary Examiner L. L. SMITH, Assistant Examiner 

